On Wednesday afternoon, 20 couples gathered in front of a stage at the National Mall in Washington to recite their commitment vows. Some brides had on white gowns while grooms wore top hats. Others donned orange T-shirts printed with the words “Disability Rights Are Human Rights.”

“We would like to get married and be able to go to the doctor,” they chanted in unison. “We would like to get married and not end up living in a cardboard box.”

Their combined voices might not have been loud enough for lawmakers at the Capitol, visible in the distance, to hear. But that, too, is something the couples and about 80 supporters who watched the Disabled Marriage Equality Now rally from lawn chairs would have liked.

“We’re here to send a message,” said Steve Way, 32, a speaker at the event who was born with Ullrich congenital muscular dystrophy. He traveled from Rutherford, N.J., in the back of a minivan with his wheelchair and breathing tubes. “Everyone should have the right to get married without compromising their health and safety.”

For many people with disabilities, marriage can be a financial trap. Those who receive Supplemental Security Income, a Social Security program for disabled people and older adults with few assets and little to no income, are at risk of losing their modest monthly stipend and the Medicaid that comes with it if they marry.

According to the Disability Rights Education and Defense Fund, the nonprofit group that organized the rally, around 7.6 million Americans receive S.S.I. About a million more are classified as disabled adult children, a designation that qualifies recipients for Medicare and a small monthly Social Security stipend. They are also at risk of losing some or all of their benefits, if they become their partners’ legal spouses.

Representative Jimmy Panetta, a Democrat from California, has proposed legislation that would remove the marriage restriction. “The current, but antiquated, law essentially penalizes people for following their hearts,” he said.

Ayesha Elaine Lewis, a staff attorney on the nonprofit’s leadership team and the event’s M.C., blames bureaucracy and outdated laws — some of which can be traced to the 1950s — for the restrictions that make marriage prohibitively or even dangerously expensive for her clients. (Medicaid covers personal attendant care and other disability-related services; private insurance may not.)

“Paternalism, low expectations and ableist assumptions are baked into these laws,” Ms. Lewis said. “We need an adjustment to reflect a reality where people with disabilities lead big, bright and audacious lives.”

As the commitment ceremony was underway, Patrice Jetter, who led the nonlegal ceremony, demonstrated maximum brightness and audacity from a stage outfitted with a towering pink-and-red heart and “End the Disabled Marriage Penalties” banners. Wearing an ankle-length tiered rainbow gown, a matching tulle headpiece and a “Love Is Love” sash draped Miss America-style across her torso, Ms. Jetter, a Special Olympian and disability rights advocate, reminded those in the audience why they had come.

“We are gathered here today in solidarity, love and togetherness to promote marriage equality,” said Ms. Jetter, who has competed in multiple sports, including bocce and figure skating. Her own wedding ceremony with her fiancé, Gary Wickham, on Aug. 20, in Princeton, N.J., was not the legal kind. It was, instead, a way to celebrate what Mr. Wickham called a “perfect as can be” life together despite government-imposed financial limitations. Both Ms. Jetter and Mr. Wickham have cerebral palsy.

Ms. Jetter, 59, is a school crossing guard in Hamilton, N.J., her hometown. The $800 a month she earns is “just enough not to mess up my S.S.D.I. payments,” she said, referring to Social Security Disability Insurance, a program similar to S.S.I.If she earned more, her benefits could be slashed. Mr. Wickham, 57, of Princeton, is retired from doing piecework, or as he described it, “different little menial jobs nobody else wants to do, so they give them to disabled people.” Marrying Ms. Jetter could compromise his ability to retain a fund that his parents saved for him to live on before they died.

For Ms. Jetter and Mr. Wickham, who uses a wheelchair, the goal of the rally was to advocate a future less fraught for couples who might otherwise have similar struggles. “We might not actually be able to get married” ever, Mr. Wickham said. “But we’d like to make a difference for other people maybe five or 10 years down the road.”

Mr. Way, a stand-up comedian and an actor on the Hulu series “Ramy,” is counting on it. Although he is single, he doesn’t intend to be forever. When he finds a partner, “I want the option, like everyone else, to get married without losing the care I need to survive,” said Mr. Way, who also works as a substitute teacher.

Julia Simko, 33, and Ray Vercruysse, 35, a couple that followed Ms. Jetter and Mr. Wickham to the rally from their homes in West Windsor, N.J., are betting on that future, too. They both live with developmental disabilities.

“We just want our happily ever after,” said Ms. Simko, her wedding veil blowing in the late-summer breeze.